Creation of Recombinant Salmonella Strains
Several methods for generating Salmonella vaccine strains expressing chromosomally integrated foreign DNA have been developed. Three such methods are: 1) specific integration into the aroC gene [Strugnell, 1990], 2) using of a defective transposable element [Flynn, 1990], and 3) specific integration into the his locus [Hone, 1988].
However, use of any of these methods results in chromosomal insertion of the recombinant genes into regions where the wild-type (original) genes are not normally found. Because of this, the native promoter region(s) cannot be utilized for expression. Therefore, the development of strategies for heterologous antigen presentation which address the use of native promoter regions and minimize genetic alterations in the host chromosome are required.